Q9 Probability (1 Viewer)

lyounamu

Reborn
St. Eve said:
how can it be 15%x2? that would mean the probability of 2/2 not owning a phone would be greater than 1/1. it is 15%x15% which is 0.0225 or 9/400
it's 0.15^2 as you said there.

Some people can get confused.

BackCountrySnow

Active Member
Timothy.Siu said:
nah, but when u pick one, and he doesn't have a phone, then the next one you pick will have a lesser chance of having a phone.
e.g.

say there are 100,000 australian students
15% dont hav a phone so 15,000
picking 2 that dont hav a phone is 0.15x14999/99999=0.0024987....
there shouldn't be replacement
when the sample space is that large, the difference is negligible and can be ignored.

daniellekho

Cool Member
the only thing that confused me about this question was why it was so easy for a question so late in the exam.

Timothy.Siu

Prophet 9
daniellekho said:
the only thing that confused me about this question was why it was so easy for a question so late in the exam.
and it was 2 marks

r.uss

Member
erm said:
ur an idiot.

The sample space is so large that the events are considered independent NOT dependent. i.e. the probability of each event will not be affected by a previous outcome.

(as you have shown us the difference is quite small anyway)
erm is right. Except I don't, for one, think you are an idiot.

Also... I'm guessing the reason it was two marks is because one step required you finding the complimentary event, non?!

Prosper

Member
Timothy.Siu said:
and it was 2 marks
This is what confused me. I had the right answer then crossed it out, thinking there was some trick....*cries*

lyounamu

Reborn
Timothy.Siu said:
and it was 2 marks
Get over it. 2 marks is nothing. No matter how easy the exam, the value of the question can be high.

Look at questions 1-5, you would have noticed tonnes of easy quesions valued higher than that.

Getting this easy question in Q9 where it is supposed to be hard shows the quality of the paper in general.

Aaron.Judd

Member
Anyway in conclusion, the answer is certainly 9/400

lyounamu

Reborn
Aaron.Judd said:
Anyway in conclusion, the answer is certainly 9/400
agreed

lyounamu

Reborn
morning storm said:
i was joking haha :S
haha, got me confused there...